The Correlationanalysis Between Infection And Pili-like Protein Gene PilA Of Enterococcus Faecium

Background Enterococcus faecium is an opportunistic pathogen, inthe past20years, infection rate cause by it increased rapidly, especially inChina, the infection rate rose faster. The intrinsic resistance of enterococcito a large number of antibiotics, higher morbidity, mortality and healthcarecosts and a growing number of vancomycin-resistant E.faecium has madetheir clinical treatment difficult. The ability of E. faecium to disseminate inthe hospital environment is thought to be due not only to the presence ofantibiotic resistance genes but also to the acquisition of determinants whichmay increase the capacity of the organism to survive in, colonize patients inthe clinical setting. Previously, a gene designated hylEfm, which encodes aprotein with homology to hyaluronidases, was postulated to be a potentialvirulence factor of clinical isolates of E. faecium. Animal models confirmthat a plasmid carrying the hylEfmgene has been previously shown to be animportant factor for gastrointestinal colonization. It is revealed that hylEfmgene may be an important virulence factor of E. faecium, but its exactmechanism is still unclear. Pilus-mediated adherence to host tissues followed by colonization of mucosal surfaces is believed to be an initialand necessary step in the onset of infection and is a prerequisite forpathogenesis. David S. Kim et al found that pilus-like structures and hylEfmpilA gene co-located with a large plasmid (pHylEfm), which prompt that pilAand hylEfmgene can transfer via plasmids, but the exact role has not beenconfirmed.Objective To investigate the relationship between pilA and thepathogenic mechanism of Enterococcus faecium.Methods Kirby-Bauer method was used to evaluate the antimicrobialsusceptibility of137Enterococcus faecium. A multiplex PCR was appliedfor the detection of hylEfm, pilA and identified by DNA sequencing. Thetransfer mode between strains of Enterococcus faecium via filter matings. S1nuclease and I-CeuI assay was performed to detect the position of pilA,hylEfmgene.Results We isolated237strains of Enterococcus faecium, including137isolates from human clinical infections,50isolates from stools ofhospitalized patients,50isolates from stools of community volunteers,While88%of clinical isolates carried pilA genes tested,15%for hylEfmandfor both.70%of the community group isolates and52%of animal isolatescarried pilA genes, neither carried hylEfm. Filter Matingconfirmed pilA, hylEfmgenes can transfer between different strains through plasmid conjugation.Southern hybridization found both of pilA, hylEfmcarried on a large plasmid, the plasmid size running between145.5kb and291kb.Conclusion Positive rate of Pilus-like structures protein genes pilA ofEnterococcus faecium isolated fromour hospitalconsistently high during thepast four years. And significantly higher than the non-clinical infectionstrains, which was positively correlated with the Infection rate. pilA, hylEfmgenes simultaneously encoded on a large plasmid containing variableantibiotic resistance genes in different isolates, and the presence of thisplasmid enhances the survival ability of nosocomial Enterococcus faeciumstrains.